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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Subcellular fraction (brush border, mitochondria, microsomes and plasma membranes) are isolated from the rat intestinal epithelial cells. A comparison was made between the effect of cold storage, freeze-thawing, heating and of some chemicals (DMSO, DTT, glycerol, sucrose) on the stability of Mg2+ and (Na+-K+) dependent ATPases in these fractions in order to determine possible difference linked to the localization in the enterocyte. Enzymatic activities were found more stable at -20 degrees C than at +4 degrees C. Microsomal (Na+-K+)-ATPase increased in activity until the 8th day, then declined. Brush border (Na+-K+)-ATPase was the least resistant of all fractions. For Mg2+-ATPase, that from mitochondria was that had lost much more activity (84%) in 15 days at +4 degrees C. With freeze-thawing there was a comparable decrease in all activities (20-35%). by heating between 35 and 60 degrees C, Mg2+-ATPase was shown to be more heat resistant than (Na+-K+)-ATPase. The addition of some stabilizing chemicals (DMSO, glycerol, sucrose) improved the heat stability of the two enzymes: better results were obtained with glycerol for Mg2+-ATPase and sucrose for (Na+-K+)-ATPase. These differences might be due to the compositon in membraine lipids or to the nature of the enzymes studied.
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PMID:Studies on intestinal adenosine triphosphatases. II. Stabilitiies in different rat subcellular fractions. 14 Aug

The properties and localization of ATPase system in nuclei of skeletal muscle of normal rabbit and of those with experimental muscle dystrophy were studied by electron cytochemistry. The product of cytochemical reaction of ATP hydrolysis, which is a marker of ATPase activity localization in nuclear ultrastructures, was detected on the nuclear membrane, in chromatin and in the nucleolus, ATPase activity in the nuclei was detected in the presence of both, Mg2+ and Ca2+. Addition to the incubation medium, originally containing Mg2+, Na+ and K+, resulted in an increased formation of the product reaction in all the nuclear ultrastructures in both in the norm and under experimental muscle dystrophy. However, specific inhibitor of Mg2+, Na+, K+-ATPase--ouabain--suggests the absence in the nuclei of skeletal muscles of rabbit of transport ATPase working in the "Na-pump" system. The results of experiments with a specific complex of Ca2+--EGTA allow to suppose that Mg2+, Ca2+-ATPase of skeletal muscle nuclei of normal rabbits is localized in the nucleoplasm, whereas Mg2+-ATPase is found on the nuclear membrane. Using EGTA we failed to detected the localization of Mg2+, Ca2+-ATPase in nuclear ultrastructures upon experimental muscular dystrophy.
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PMID:[Electron-cytochemical study of the localization and properties of ATPases in the isolated nuclei of rabbit skeletal muscle under normal conditions and in experimental muscular dystrophy]. 14 28

The influence of various bile acids on the (Na+-K+)-ATPase and Mg2+-ATPase activity of rat colon is described. At a concentration of 0.6 mmol/l C and TC did not inhibit the (Na+-K+)-ATPase activity in contrast to GC. The taurine derivates TC, TCDC and TDC did not influence or even enhanced the (Na+-K+)-ATPase activity. All bile acids except C, TC and CDC depressed the Mg2+-ATPase activity. At higher concentrations only C and TC did not influence the (Na+-K+)-ATPase activity. C, GC and TC at 2.5 mmol/l decreased the (Na+-K+)-activated phosphatase with ATP as substrate. All other substrates tested did not influence the enzymic activity significantly. The results indicate that bile acids can inhibit the Na+-absorbing system in rat colon. Hence this inhibition can cause diarrhea.
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PMID:Influence of bile acids on the (Na+-K+)-activated- and Mg2+-activated ATPase of rat colon. 14 61

The synthesis, proof of structure, and biological activity of some new steroidal 17beta-formyl guanylhydrazones are described. The guanylhydrazones of nondigitalis-like steroids inhibited myocardial Na+,K+-ATPase but had only a depressant effect on myocardial contractility. By comparison, the corresponding guanylhydrazone of a digitalis-like steroid gave a positive inotropic effect in concentrations that also inhibited Na+,K+-ATPase. The nondigitalis-like guanylhydrazones also inhibited membrane Mg2+-ATPase and this may infer that the compounds act nonspecifically by membrane stabilization rather than by interaction with stereoselective receptors. Biological activity was determined in the guinea pig.
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PMID:Cardenolide analogues. 7. Synthesis and biological activity of some new steroidal guanylhydrazones. 14 38

Effects of commonly used purification procedures on the yield and specific activity of (Na+ + K+)-ATPase (Mg2+-dependent, Na+ + K+-activated ATP phosphohydrolase, EC 3.6.1.3), the turnover number of the enzyme, and the kinetic parameters for the ATP-dependent ouabain-enzyme interaction were compared in canine brain, heart and kidney. Kinetic parameters were estimated using a graphical analysis of non-steady state kinetics. The protein recovery and the degree of increase in specific activity of (Na+ + K+)-ATPase and the ratio between (Na+ + K+)-ATPase and Mg2+-ATPase activities during the successive treatments with deoxycholate, sodium iodide and glycerol were dependent on the source of the enzyme. A method which yields highly active (Na+ + K+)-ATPase preparations from the cardiac tissue was not suitable for obtaining highly active enzyme preparations from other tissues. Apparent turnover numbers of the brain (Na+ + K+)-ATPase preparations were not significantly affected by the sodium iodide treatment, but markedly decreased by deoxycholate or glycerol treatments. Similar glycerol treatment, however, failed to affect the apparent turnover number of cardiac enzymes preparations. Cerebral and cardiac enzyme preparations obtained by deoxycholate, sodium iodide and glycerol treatments had lower affinity for ouabain than renal enzyme preparations, primarily due to higher dissociation rate constants for the ouabain.enzyme complex. This tissue-dependent difference in ouabain sensitivity seems to be an artifact of the purification procedure, since less purified cerebral or cardiac preparations had lower dissociation rate constants. Changes in apparent association rate constants were minimal during the purfication procedure. These results indicate that the presentyl used purification procedures may alter the properties of membrane (Na+ + K+)-ATPase and affect the interaction between cardiac glycosides and the enzyme. The effect of a given treatment depends on the source of the enzyme. For the in vitro studies involving purified (Na+ + K+)-ATPase preparations, the influence of the methods used to obtain the enzyme preparation should be carefully evaluated.
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PMID:Membrane (Na+ + K+)-ATPase of canine brain, heart and kidney. Tissue-dependent differences in kinetic properties and the influence of purification procedures. 14 5

(Na+ + K+)-ATPase activity is demonstrated in plasma membranes from pig mesenteric lymph nodes. After dodecyl sulfate treatment plasma membranes have an 18-fold higher (Na+ + K+)-ATPase activity, while their ouabain-insensitive Mg2+-ATPase is markedly lowered. A solubilized (Na+ +K+)-ATPase fraction, obtained by Lubrol WX treatment of the membranes, has very high specific activity (21 mumol Pi/h per mg protein). Concanavalin A has no effect on these partially purified (Na+ + K+)-ATPase, while inhibits (40%) this activity in less purified fractions which still contain Mg2+-ATPase activity.
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PMID:Studies of (Na+ + K+)-sensitive ATPase activity in pig lymphocytes. Effects of concanavalin A. 14 92

The activities of Ca2+, Mg2+-ATPase and Na+, K+-ATPase and the permeability of reconstituted human erythrocytes for Na and K ions were measured, using Ca2+-EGTA, Ca2+ATP and Ca2+-sodium citrate buffers. It was found that the increase in the Ca2+/chelate ratio caused stimulation of Ca2+, Mg2+- and Na+, K+-Atpases and an increase in the rate constants of ouabain--dependent 42K+ influx and 22Na+ efflux from the erythrocytes. The use of the Ca2+-sodium citrate system as a calcium buffer did not change the parameters of the functional state of erythrocyte membranes. The data obtained are discussed in terms of a possible role of calcium ions, which are bound to the inner surface of the erythrocyte membrane, in the regulation of the systems of active and passive transport of cations.
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PMID:[The effect of membrane-bound calcium on the activity of adenosine triphosphatase from erythrocytes and erythrocyte permeability for monovalent cations]. 14

Calcium transport from red cells was measured in seventeen patients with congenital or hereditary spherocytosis (HS). The efflux remained at a lower level in resealed ghost cells of patients than in normal cells both in the presence and absence of adenosine triphosphate (ATP). We studied the activities of Ca2+,Mg2+-ATPase, ouabain-sensitive Na+,K+-ATPase, Mg2+-ATPase and Ca2+-(spectrin-)ATPase in cell membranes prepared by washing the cells with hypotonic medium. The mean +/-SD Ca2+,Mg2+-ATPase/Mg2+-ATPase of HS patients was 3.34 +/- 1.06, and 2.81 +/- 0.42 in control subjects. Na+,K+-ATPase/Mg2+-ATPase was 2.38 +/- 0.38 in HS cells compared to 2.01 +/- 0.41 in normal cells. Ca2+-ATPase/Mg2+-ATPase of HS membranes was 0.57 +/- 0.18 and the control value 0.43 +/- 0.08. These data indicate calcium retention in the erythrocytes of HS patients in spite of increases in Ca2+,Mg2+-ATPase activity in the majority of patients.
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PMID:Calcium transport and adenosine triphosphatase activities of erythrocyte membranes in congenital spherocytosis. 14 26

The article deals with the influence of sodium dodensylsulfate, lubrol and also of inhibition of Na+,K+-ATPase and Mg2+-ATPase activities by N-ethyl malemid on the form of curves of erythrocyte membranes amperometric titration by Ag+. It is shown that changes in a conformational structure of proteins membranes under the influence of detergents results in the transformation of SH-group of type I to SH-groups of type II. A 70% fall of Na+,K+-ATPase activity has the same result. So, the form of the curves for titration of erythrocyte membranes sulphydryl groups may serve as an indicator to the morpholocial and functional state of the membranes protein part.
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PMID:[Influence of detergents and inhibition of Na+,K+-ATPase and Mg2+ATPase on erythrocyte membrane SH-groups]. 14 2

The regulation of adrenergic receptors in rat heart was measured in rats made hyperthyroid by injection with thyroxine and made hypothyroid by addition of propylthiouracil to the drinking water. Hyperthyroid rats display cardiac hypertrophy and a decrease in epididymal fat pad weight. The maximal beta-receptor level of ventricular membranes, as determined by (-)-[3H]dihydroalprenolol binding, was increased 60% by thyroxine treatment and decreased about 30% by propylthiouracil treatment. The affinity of the beta receptor was unchanged after thyroxine or propylthiouracil treatment. The maximal activity of the isoproterenol-stimulated adenylate cyclase (EC 4.6.1.1) varied with thyroid state in a manner parallel to the increase in beta-adrenergic binding sites. Thyroxine treatment also increases by 2-fold the beta receptors in isolated rat fat cells. Propylthiouracil treatment lowered the level of alpha receptors in heart by 30% as measured by [3H]dihydroergocryptine binding, but increased the affinity about 2.5-fold. The highest level of alpha receptors was seen in control hearts. These studies indicate that thyroxine may control the turnover of beta-adrenergic receptors in heart and fat cells and regulate physiological responses in these tissues via a hormone-hormone interplay system. Thyroxine treatment reduced the activity of the membrane-bound Mg2+-ATPase (EC 3.6.1.3) and 5'-mononucleotidase (EC 3.1.3.5) but appears to increase the activity of the (Na+ + K+)ATPase (EC 3.6.1.4).
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PMID:Hormone action at the membrane level. VIII. Adrenergic receptors in rat heart and adipocytes and their modulation by thyroxine. 14 63


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